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200-201 Practice Question: During incident response, a security analyst…
During incident response, a security analyst reviews a PCAP file and sees TCP packets with only the SYN flag set, followed by RST packets upon receiving a SYN-ACK. No connection is established. Which scanning technique is being used?
⚠ Common exam trap
Cisco often tests the distinction between a half-open scan and a full connect scan by focusing on whether the three-way handshake is completed; the trap here is that candidates may confuse the RST sent after SYN-ACK as part of a normal connection teardown, rather than recognizing it as the defining characteristic of a SYN scan that never completes the handshake.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Half-open scan (SYN scan)
The described behavior—sending a SYN packet, receiving a SYN-ACK, and immediately replying with an RST—is the hallmark of a half-open (SYN) scan. This technique never completes the three-way handshake, so the target does not log an established connection, making it stealthier than a full connect scan. The RST sent after the SYN-ACK terminates the handshake before it can be fully established, confirming the port is open without creating a full session.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Half-open scan (SYN scan)
Why this is correct
Half-open scan sends SYN, receives SYN-ACK, then RST to avoid detection.
- ✗
FIN scan
Why it's wrong here
FIN scan uses FIN packets, not SYN.
- ✗
Christmas tree scan
Why it's wrong here
Xmas scan sets FIN, PSH, and URG flags, not just SYN.
- ✗
Full connect scan
Why it's wrong here
Full connect scan completes the TCP handshake, but the observed pattern has no ACK.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-201 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-201 exam.